The disclosure relates to a transmitting communication apparatus and a receiving communication apparatus of a non-coherent communication system. The transmitting communication apparatus is configured to communicate with the receiving communication apparatus via a communication channel. The transmitting communication apparatus comprises a processing circuitry configured to: map a sequence of data bits into a modulation symbol of a plurality of modulation symbols defined by a modulation constellation, wherein the modulation constellation is defined by a tiling of a Grassmannian manifold into a plurality of cells and a Cartesian product of a plurality of auxiliary constellations, wherein the Cartesian product of the plurality of auxiliary constellations is mapped onto each cell of the plurality of cells and each auxiliary constellation defines a plurality of auxiliary symbols. The processing circuitry is further configured to transmit a modulated signal based on the modulation symbol via the communication channel to the receiving communication apparatus.